 Stem cells have two features, self-renewal and multilineage differentiation. Embryonic stem cells are associated with tumor genesis and ethical considerations, while adult mesenchymal stem cells are less problematic. MSCs can be isolated from various tissues and have been found in new sources. The mechanisms of differentiation, mobilization, and homing of MSCs are complex, making them an attractive choice for clinical applications. Future studies should explore the role of MSCs in disease treatment. This article was authored by Da Qingding, Wei Chengxiu, and Xinzong Lin-MD, PhD.